Ivanka Trump expressed some disagreement with her father on one aspect of the impeachment inquiry during an interview with the Associated Press published on Friday morning.

The First Daughter and top White House adviser disagreed with her father — and boss — about the importance of naming the whistleblower who complained about his July 25 call with the Ukrainian president. Ivanka Trump said that the whistleblower's identity is "not particularly relevant" to the inquiry.

"The whistleblower shouldn't be a substantive part of the conversation," she said. "This is a third party who was not privy to the call and did not have firsthand information. That is what was the catalyst for all of this discussion. But to me, it's not particularly relevant aside from what the motivation behind all of this was."

President Trump has been demanding to know the whistleblower's identity and calling for the person to testify in public, even though federal law gives whistleblowers the right to remain anonymous.

The pressure initially drove the whistleblower to make some concessions last week. The person offered to answer written questions directly from Republicans on the House Intelligence Committee — on the condition that his or her identity would still be hidden but verified by the inspector general of the intelligence community.

But Mr. Trump quickly rejected that idea, and House Republicans have hardly commented on it.

Then on Friday, the whistleblower's attorney, Mark Zaid, sent a cease-and-desist letter to White House counsel Pat Cipollone, warning that Mr. Trump's "rhetoric and activity" have put his client and client's family in danger.

CBS News obtained a copy of the letter, which was first reported by CNN, and which enumerates statements made by Mr. Trump that Zaid argues "seek to intimidate my client — and they have."

Zaid said the comments amount to "tampering with a witness or informant," which is a violation of the law.